MicroRNAs (miRNA) are small, non-coding RNA molecules, which play a critical role in gene regulation and thus influence important biological processes such as development, cell proliferation, and cell death. To prevent possible occurring degradation of RNA molecules, only exosomal miRNA in the blood serum was taken into account. Exosomes are cell-derived vesicles that are present in many eukaryotic fluids, including blood.
Mice were exposed to magnetic flux densities of 0.1 mT, 0.5 mT, or 2.5 mT (n=100, respectively). For each magnetic flux density, a corresponding control group, also consisting of 100 mice each, was examined. At each time point (after 0, 1, 10, 30, and 90 days), 20 mice per group were killed and blood was collected.
|Exposure duration||8 hours/day for 1, 20, 30, or 90 days|
|Chamber||exposed and control group and were housed in standardized cages (10 mice per cage); all cages were placed in the same room|
|Setup||a transformer was used to power the coils for generating the magnetic field; homogenous region of magnetic field was 0.4 × 0.4 × 0.4 m; magnetic field was measured inside the cage and kept constant, independent of the position|
|Sham exposure||A sham exposure was conducted.|
In blood serum exosomes from exposed mice, 13, respectively 3 and 5 miRNAs were identified, which were expressed dose-specifically at 0.1 mT, 0.5 mT and 2.5 mT, respectively. Furthermore, five miRNAs were found to be common for magnetic field exposure regardless of the magnetic flux density. Further analysis revealed that the differentially expressed miRNAs of all groups (at the individual flux densities, i.e. 0.1, 0.5, 2.5 mT as well as expressed at all flux densities, i.e. "common") are related with the neural system and regulation of transcription and gene expression. However, the related signal pathways were quite different between the groups (0.1, 0.5, 2.5 mT and "common").
Quantitative real-time PCR revealed that the gene expression of miR-128-3p was significantly upregulated in exosomes from exposed mice (all magnetic flux densities) compared to those from control mice, while miR-133a-3p, miR-142a-5p, miR-218 and miR-199 were significantly downregulated.
The authors conclude that they found dose-specific and common exosomal miRNA markers for the exposure of mice to 50 Hz magnetic fields.